Communicating your mental model to the user: Design models and the system image

As a user interface designer, you’ll have a conceptual mental model in your mind of how the application works. In order for a user to be able to operate the application effectively, she will have to have a similar mental model in her mind.

One way of building up a mental model in a user’s head is to provide documentation such as a training manual or tutorial. The vast majority of users will never read documentation, however.

For enterprise systems in an organizational setting, you can have your users sit through a training program, but the effectiveness of corporate training varies. The motivation of employees to pay attention and learn is often low, and for training on complex applications, classroom sessions without hands-on practice are essentially useless if you want staff to understand and retain the material.

Some users have the benefit of being able to watch other users use the application, and this can be a very effective way of learning the basic concepts and understanding how to perform tasks. Having an expert nearby whom the user can ask for assistance is also very helpful.

But without any training, documentation, or opportunities to watch and ask other users, the only way a user can figure out how to use the application is to simply start using it. She will learn how to operate the application by trial-and-error. The visual presentation of the application’s user interface provides cues as to how to accomplish tasks, and the behavior of the application provides feedback on whether the tasks are being performed correctly. By exploring and experimenting with the application, the user gradually builds up a mental model of how the application works, and, with time and experience, the user’s mental model will (hopefully) increasingly approximate the designer’s mental model.

To use the terminology popularized by Donald Norman in The Design of Everyday Things, the conceptual model in the designer’s mind is called the design model. The user’s mental model is simply referred to as the user’s model. And the presentation and behavior that the product’s user interface exhibits is called the system image.

And so to design a usable and learnable product, then, the designer’s challenge can be viewed as aligning the design model and the system image, and structuring the system image in such a way that it accurately portrays the design model and enables the user to develop her own user’s model that closely approximates the designer’s model. As the completeness and correctness of the user’s model increases, the user’s skill at operating the application will approach that of the application’s designer.

Structuring the system image to make an application learnable and understandable is tricky, and the fundamental aim of this blog and the upcoming book Designing Usable Apps is to explain how to do this by means of design principles and techniques, and usability testing and evaluation techniques.

My book, Designing Usable Apps, is now available!

Welcome!

Hi, I'm Kevin Matz, founder of Winchelsea Systems Ltd. and creator of the ChapterLab word-processing app. This is my blog about usability and UX design for websites and software products. Let me know what you think!